Counter with closure in JavaScript
JavaScript interview exercise on Functions, difficulty 2 of 3. Solve it in the editor beside a worked example; the tests run the moment you do.
Write makeCounter(start = 0) that returns an object with inc(), dec(), and value() methods sharing private state. inc and dec return the new value.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Progress is saved in your browser, and in your account if you sign in.